Discussion Forum

Hi,

Currently I would like to obtain the magnetic field and eddy currents distributions inside and around a conductive (and possibly permeable) tube plunged in an oscillating axial magnetic field in the low frequency domain (0.01-100 Hz). I am working in 2D axisymmetric domain and magnetic field in frequency domain. The field is set via the Magnetic field background field option to 10 mT.

To check my implementation, I first simulated a small copper cylinder of external radius rCyl=1 cm and internal radius of 0.5 cm, the length is 2 cm. With this cylinder I could compare Comsol results to some published ones and they are in good agreement.

Then I implemented an aluminum tube with much larger dimensions: external radius of rCyl=0.6 m, 2 cm thickness and length of 12 m. For such a geometry, I have to modified the meshiing phase a bit. I look at results for the real and imaginary parts of the Br and Bz components as well as the field modulus along the tube axis and a generatrix located at 1.17x rCyl, i.e. outside the tube. As in the case of the short copper tube, I am expecting the field to become again 10 mT at some z away from the tube. Unfortunately, I obtain field which plateau at some values at large z, but do not reach the background field value as shown for B modulus on the attached plot.

I am certainly doing something wrong thus if anyone have some indications, please let me know.

Thanks a lot for any help,

Gilles